Tire tread

ABSTRACT

A pneumatic tire is provided with a tread having a traction pattern consisting of grooves. The tread pattern inhibits stone penetration within the tread by suspending or cradling the stone spatially from the bottom of the groove. The grooves are provided with transverse crossbars or buttresses having a configuration and dimension relative to the groove to support or cradle a stone above the bottom of the groove.

United States Patent [191 Hoke [ TIRE TREAD [75] Inventor: Gilbert .1.Hoke, Kenmore, NY.

[73] Assignee: Dunlok Tire and Rubber Corporation, Buffalo, NY.

[22] Filed: Feb. 18, 1971 [21] Appl. No.: 116,328

Related US. Application Data [63] Continuation-impart of Ser. No.750,387, June 27,

1968, abandoned.

[52] US. Cl ..l52/209 [51] Int. Cl ....B60c 11/10 [58] Field of Search..l52/209 [56] References Cited UNITED STATES PATENTS 2,268,344 12/1941Shesterkin 152/209 51 Apr. 17, 1973 3,095,024 6/1963 Robertson 152/2092,327,057 8/1943 Ofensend 2,736,797 7/ 1956 Campbell 2,938,560 5/1960Wallace 152/209 Primary Examiner-Gerald M. Forlenza AssistantExaminer-D. W. Keen Attorney-Rauber & Lazar and Eliot S. Greber [57]ABSTRACT A pneumatic tire is provided with a tread having a tractionpattern consisting of grooves. The tread pattern inhibits stonepenetration within the tread by suspending or cradling the stonespatially from the bottom of the groove. The grooves are provided withtransverse Crossbars or buttresses having a configuration and dimensionrelative to the groove to support orcradle a stone above the bottom. ofthe groove.

17 Claims, 15 Drawing Figures PATENTEU 3.727. E561 INVENTOR. GIL BERTJ'- HOKE 3 4 rmnmsxs Ebb/v) SHEET 2 BF 3 ENTOR. a/z BERT HOKE ATTORNEYSTIRE TREAD This application is a continuation-in-part of US. applicationSer. No. 750,387, now abandoned filed June 27, 1968, having the sametitle.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to pneumatic tires and in particular to the traction pattern ofthe tire tread wherein the grooves are arranged to minimize or preventtire damage from stone pick-up and stone penetration.

2. Description of the Prior Art The rubber treads of pneumatic tiresarecommonly provided with a plurality of transversely spacedcircumferentially continuous, relatively narrow, anti-skid grooves toincrease the traction properties and flexibili ty of the treads. Suchgrooves are commonly made circumferentially straight or of a tortuousshape, i.e., zigzag, sinuous, etc.

The grooves of a tortuous shape are considered preferable because such ashape provides a much greater groove edge effective for increasing thetraction and anti-skid properties of the tread, and also presents thegroove edges in various directions so as to increase the traction andanti-skid properties in all directions.

A problem with respect to the large grooves is that they permit foreignobjects, such as stones, to enter into the groove early in the tireslife. The depth of the deep grooves allows the stones to be held ortrapped by the compression of the rubber in the sides or walls of theribs formed by adjacent grooves. Eventually the stones are forcedagainst the bottom of the groove by pressure of the load on the tire androad surfaces. As the tire wears, the stone is subjected to additionalpressure as the depth of the tread rubber decreases or another stone maybe trapped above the original one, exerting pressure on the first stone.If the lodged stone has a point or sharp edge, the pressure may causethe stone to cut through or split the bottom of the groove to penetratethe under tread rubber and the cords of the tire s carcass.

' The grooves, thus, have occasioned annoyance and damage as the resultof picking up or holding stones and other hard objects of various sizesand dimensions. Problems relating to the grooves still remain,notwithstanding the many designs of grooves heretofore proposed.

It is the general object of this invention, therefore, to improve thetraction pattern of pneumatic tires with respect to the deleteriouseffects of stones entering the groove.

SUMMARY OF THE INVENTION According to the invention, there is provided apneumatic vehicle tire having a traction-pattern in the tire treadprovided with grooves generally extending radially inwardly from thesurface of the tire tread.

The grooves are provided with crossbars extending transversely acrossthe bottom portion of the groove. The crossbars may be horizontal orparallel with respect to the tread surface merging with orperpendicularly into the side walls of the grooves. The crossbars mayalso extend upwardly forming buttresses against the side walls of thegrooves as a crescentshaped crossbar merging gradually or tapering intothe side wall spatially below, i.e., radially inwardly, of the treadsurface. Furthermore, the crossbar may extend along the side wall of thegroove to the tread surface forming in profile a U-shaped crossbar,preferably with the upper portions slightly tapered. The cross sectionof the crossbars may be in rectangular, curved or triangular form. Thespacing between the crossbars is equal or less than the width of thecrossbars.

Foreign objects of significant size, such as stones, that may penetratethe groove are suspended within the groove by being cradled by one ormore adjacent crossbars. This suspension prevents the stone frompenetrating deeper into the groove and eventually damaging the base ofthe groove by cracking the bottom or corners thereof or tearing furtherinto the tread rubber, eventually tearing or rupturing the carcasscomprising the cords thereof. Such damage causes premature tire failure,such as blow-outs, or otherwise renders the tire unfit for recapping orretreading.

BRIEF DESCRIPTION OF THE DRAWINGS The nature of the invention ishereinafter further ex-' plained in greater detail with reference to theaccompanying drawings, forming a part of this application, in which:

FIG. 1 is a perspective view, partly in section, of a pneumatic tireprovided with a tread pattern according to the invention, having eitheror both the grooves and sipes;

FIG. 2 is a plan view of a portion of a groove according to theinvention;

FIG. 3 is a sectional view of the groove taken on the section indicatingline 3-3 of FIG. 2;

FIG. 4 is a sectional view of the groove taken on the section indicatingline 4-4 of FIG. 2;

FIGS. 5 and 6 are sectional views of the above similar to FIG. 3,showing a modification of the crossbars in the grooves;

FIGS. 7 and 8 are sectional views similar to FIG. 4,

showing other forms of crossbars in'the grooves;

FIG. 9 is a plan view of the groove showing another example of the tiregroove of the invention wherein the crossbars. are arranged in analternate configuration, buttressing the respective opposing walls ofthe groove;

FIG. 10 is a sectional view of the groove taken on sectional line 10-l0of FIG. 9',

FIGS. 11 and 12 are sectional views similar to FIG. 10 showing alternateforms of the crossbars in the tire groove; and

FIGS. l3, l4 and 15 show plan and longitudinal and transverse sectionalviews of a typical tire tread with the various size and spacingdimensions required for cradling a given size of foreign particle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings andin particular to FIG. 1, there is shown a section of a pneumatic tireincorporating in the rubber tread 10 thereof several anti-skid I grooves16 and several sipes 20 formed in accordance with the present invention.While only several grooves provided.

The tire illustrated is otherwise of conventional construction andincludes, in addition to the rubber tread l0, rubber side walls 14, afabric carcass l2 and annular bead wire bundles 13 to which the carcassis anchored during molding and vulcanizing of the tire. The tire may befabricated and molded in a conventional manner and the antiskid grooves16 and sipes 20 are preferably formed in the tread during moldingthereof. The term rubber is used to denote natural rubber, syntheticrubber and blends thereof.

The groove 16, according to the invention, is provided with a pluralityof crossbars 18 as shown in FIGS. 2, 3 and 4. The crossbars arepreferably integrally formed from the bottom of the groove 16 and extendacross the groove from one side wall to the other. The

crossbar 18a of FIGS. 3 and 4 is of the form that is generally parallelwith the tread-surface 11. Various combinations of the-width W to depthH ratio can be used, depending upon the groove width G and depth (D,FIG. 3) used. The spacing S (FIG. 2) between the crossbars 18 should besuch as to assure the suspension of the stones or other foreign objectsthat may penetrate the groove and be retained therein. The stone isthereby cradled above the bottom of the groove by one or more of thecrossbars.

According to the invention, the spacing 19 having a dimension S (FIG. 2)between the crossbars 18 should be not more than, and preferably lessthan, the width G (FIG. 3) of the groove. The width W of the crossbarwill be selected in relation to its height H, and these dimensionsrelative to the groove width G and depth D are determined in accordancewith design requirements within the guidelines to be explained.

As well known and understood in this art, groove width and depthdimensions in a pneumatic tire tread (voids between rubber ribs or lugs)differ greatly in various types of tires, i.e., from very narrow andshal low in bicycle and auto tires to very wide and deep in large truckand earthmover tires. The groove dimensions may vary within a tiretread. Thus, grooves located at or near the center of a tire tread maybe wider or narrower, deeper or shallower than the grooves located at ornear the outer edges of the tire tread. The groove dimensions also varywhen an identical tread design pattern is applied to various sizes in atire range; for example, identical patterns for mini-cars, limousines,buses and trucks still require different groove dimensions for each ofsuch type tires which vary in size.

In order to provide some degree of protection from stones and otherforeign objects causing damage to the bottom or base of the grooves inany of the above types of tires, the rubber configurations within thegrooves must be adequate in size and in some relation to the size of thegroove opening. Since the groove width determines the size of stoneaccepted and retained within the groove walls, the groove width is usedas a basis for determining the size and spacing of the crossbar elementsnecessary to resist the stone and keep it away from the groove bottomwhere the damage is done.

To determine the dimensional limitations of appropriate stone cradlingcrossbar elements in the many tire types that may be able to utilize thepresent invention, certain relationships of the size and spacing of thestructural portions of the groove are required.

Referring now to FIGS. 13, 14 and 15, there is shown a typical grooveadapted to provide the stone cradling structure according to theinvention. The various portions of the groove previously described aboveare shown in their respective dimensional relationships. The crossbarunit pitch length P, as designated in FIG. 15, is the sum of onecrossbar width W and one spacing or void width S between the crossbars.Thus, the pitch P is defined as one crossbar and the spacing betweeneach crossbar, the combination of W and S being repeated as a continuingseries is desired. The crossbar height H, shown in FIG. 15, representsthe height of the crossbar from the bottom of the groove. D

is the depth of the groove from the bottom thereof to the tread surface1 l, and G is the groove width as previously described.

According to the invention, the pitch P should be no less thanone-eighth inch and no greater than twice the groove width G. Inaddition, the crossbar width W should be no less than 50 percent and nogreater than percent of the pitch length P. The spacing or void Sbetween the crossbars should be no less than 10 percent and no greaterthan 50 percent of the pitch length P, while the crossbar height Hshould be no less than one-sixteenth inch high and no greater than 50percent of the depth D. In general, the crossbar width W will always beat least equal to or greater than the space between them, that is, thespace defined by dimension S. Further, the space S should never begreater than the groove width G.

A stone 24, shown in dotted lines in FIGS. 3 and 4, which may havepenetrated or been forced into the groove 16 and retained therein, isshown suspended or cradled from the bottom of the groove by the severalcrossbars 18a. The dotted line portions of the stone 24 in the tread 10(FIGS. 3 and 4) indicate the form of the groove and the crossbar owingto the presence of the stone. Although the position of the stone 24 maybe only temporary, since further movement of the tire over the road mayeventually cause the stone to be ejected, it will be appreciated thatthe stone 24 can nevertheless be suspended or cradled in that position'and the inner wall portions of the grooves should 4 preferably be suchthat: (a) the width W of the cross bars is of the same order ofmagnitude as the particles, and (b) the spacing between the crossbars Sis no greater than the width W. The spacing S between the crossbars ismeasured at the base of the groove or at the top of the crossbar.

A modification of the crossbars of the invention is shown in profile inFIG. 5, in a view otherwise similar to FIG. 3. The crossbars, for thisform indicated as 18b, are crescent-shaped, disposed, as a rib,laterally across the bottom of the groove and extending radiallyoutwardly from the bottom of the groove and against both side walls,serving, in effect, as buttresses thereof and terminating at the sidewalls at a place below the tread surface 11. Such buttresses may also bearranged to terminate at the surface of the tread which surface mayextend inwardly of the groove. Also, the crossbar may be a full ribextending throughout the walls of the groove, terminating at the treadsurface and having a uniform height and width. Such a form 18b is shownin FIG. 6. The dotted lines indicate a taper of the upper portion of thecrossbar that may be provided. Such forms of crossbars provide V-shapedor U-shaped cradles or suspension structure for stones which preventsthereby deeper penetration of the stone and which eventually may effectrejection of the stone radially outward from the groove. It should beespecially noted, as above indicated, that the stone need not be ejectedfrom the groove. Indeed, the stone may be retained in position, cradledharmlessly from the bottom of the groove throughout the life of thetire, by the crossbar and the side walls of the groove.

It will be appreciated that'the crossbars according to the inventioneffectively extend the useful depth of a groove which depth wouldotherwise be prohibitive if, for example, the remaining tread rubber tothe carcass were critically thin. Groove channel depth of the nonskidtype can thus be made to more desirable depths than heretofore forlonger-life-traction requirements and yet obviate the damage caused bystones.

Referring now to FIGS. 9 through 11, there is shown other forms ofcrossbars according to the invention shaped as buttresses disposedalternately respectively to opposite walls along the longitudinaldirection of the groove. The crossbars 26a and 26b extend from one lowerside wall portion of the groove 16 laterally across the groove and slopeupwardly into the opposite wall, merging therein at a location spatiallyradially inwardly from the tread surface 11. The upper surface 27 of thecrossbars 26a and 26b may be curved outwardly in profile, as shown inFIG. 10, or may be linear 29 as shown in FIG. 11 for the crossbars 28aand 28b. The alternating crossbars may also be arranged to extend totread surface 11 as shown in FIG. 12. The crossbars 30a and 30b curvefrom a lower portion of one side wall of the groove 16 upwardly acrossthe groove to the plane of the tread surface and connect to the oppositeshown in FIGS. 4, 7 and 8 as described above with respect to thecrossbars of FIGS. 3, 5 and 6.

It will now be appreciated that the grooves according to the inventionserve to inhibit, if not substantially prevent, the retention of foreignobjects, such as stones that may be picked up, and the consequentpenetration of such objects deep into the tire tread to fracture thetread or otherwise damage the carcass. Any stones that are retained inthe groove are cradled harmlessly from the bottom thereof. Furthermore,as the tread surface wears, the crossbars will serve as additionaltraction edges to thereby prolong more effectively the tractionlife ofthe tire.

Although several preferred forms of the invention have been described,it will be apparent that modifications may be made therein by thoseskilled in the art without departing from the scope of the invention asset forth in the appended claims.

I claim:

1. A tire tread having a traction pattern including grooves, crossbarsextending laterally across the bottom of said groove and the spacingbetween said crossbars being no greater than the width of said grooves,

wherein alternate crossbars extend respectively from opposite walls ofsaid grooves inwardly from the tread surface and slope downwardly andoutwardly from one wall terminating in the surface of the opposite wallradially outwardly from the bottom of said groove.

2.A tire tread having a traction pattern including.

grooves, crossbars extending laterally across the bottom of saidgrooves, and the spacing between said crossbars being no greater thanthe width of said grooves, a recess defined by the tops of saidcrossbars and the inner wall portions of said groove for receivingspacing between the said crossbars being at least 10 percent and nogreater than 50pereent of said unit pitch length, and the height of saidcrossbars being the measurement between the groove: bottom and the outerextremity of said crossbars and said height of said crossbars being atleast one-sixteenth inch and no greater than 50 percent of the depth ofsaid grooves.

3. A tire tread according to claim 2 wherein the upper surface of saidcrossbars is parallel with the tread surface and spaced inwardly fromthe tread surface.

4. A tire tread according to claim 2 wherein the ends of said crossbarsslope upwardly tapering and merging into the side walls of said groovesbeing formed generally in crescent-shaped cross-section transverse ofsaid groove.

5. A tire tread according to claim 2 wherein said crossbars aretriangular in cross-section, the apex of which triangle being disposedradially outwardly from the base of the groove.

6. The tire tread according to claim 2 wherein the surface of saidcrossbars is generally curved.

7. A tire tread according to claim 2 wherein at least one end of theradially outer surface or extremity of at least one of the crossbarsextends radially outwardly to merge gradually with the wall of thegroove.

8. A tire tread according to claim 2 wherein at least one of thecrossbars extends across the wall of the groove and is generallyU-shaped in cross-section trans verse to the groove.

9. A tire tread according to claim 2 wherein the depth of the U-shapedcrossbar gradually decreases towards its junction with the wall of thegroove adjacent to the tread surface.

10. A tire tread according to claim 2 wherein the radially outersurfaces or extremities of alternate crossbars extend respectively fromopposite walls of the groove radially inwardly from a junction of thesaid surfaces or extremities of the crossbar with the wall of the grooveadjacent to the tread surface.

11. A tire tread according to claim 10 wherein the radially outersurfaces or extremities of alternate crossbars extend from a junctionwith the wall of the groove spaced from the tread surface.

12. A tire tread according to claim 10 wherein the radially innersurface of the two junctions of the radially outer surface or extremityof the crossbar with the walls of the grooves is spaced apart from thegroove bottom.

13. A tire tread according to claim 2 wherein at least one of saidcrossbars is rectangular in cross-section.

14. A tire tread according to claim 2 wherein at least one end of theradially outer surface or extremity of at least one of the crossbarsextends radially outwardly to merge gradually with the wall of thegroove.

15. A tire tread having a traction pattern including grooves, crossbarsextending laterally across the bottom of said grooves, and the spacingbetween said crossbars being no greater than the width of said grooves,a recess defined by the tops of said crossbars and the inner wallportions of said groove for receiving without retaining particles, thespacing between said crossbars being no greater than the width of saidcrossbars, said spacing being measured either at the base of the grooveor at the top of the crossbar, whereby particles of size greater thanthe spacing between the crossbars are cradled from the bottom of saidgroove and smaller particles which may enter said recess are notretained therein, and wherein the radially outer surfaces or extremitiesof alternate crossbars extend respectively from opposite walls of thegroove radially inwardly from a junction of the said surfaces orextremities of the crossbars with the wall of the groove

1. A tire tread having a traction pattern including grooves, crossbarsextending laterally across the bottom of said groove and the spacingbetween said crossbars being no greater than the width of said grooves,wherein alternate crossbars extend respectively from opposite walls ofsaid grooves inwardly from the tread surface and slope downwardly andoutwardly from one wall terminating in the surface of the opposite wallradially outwardly from the bottom of said groove.
 2. A tire treadhaving a traction pattern including grooves, crossbars extendinglaterally across the bottom of said grooves, and the spacing betweensaid crossbars being no greater than the width of said grooves, a recessdefined by the tops of said crossbars and the inner wall portions ofsaid groove for receiving without retaining particles and the spacingbetween said crossbars being no greater than the width of saidcrossbars, the unit pitch length defined as the sum of the width of eachof said crossbars and the spacing between said crossbars being at leastone-eighth inch and no greater than twice the width of said grooves, thewidth of said crossbars being at least 50 percent and no greater than 90percent of said unit pitch length, the spacing between the saidcrossbars being at least 10 percent and no greater than 50 percent ofsaid unit pitch length, and the height of said crossbars being themeasurement between the groove bottom and the outer extremity of saidcrossbars and said height of said crossbars being at least one-sixteenthinch and no greater than 50 percent of the depth of said grooves.
 3. Atire tread according to claim 2 wherein the upper surface of saidcrossbars is parallel with the tread surface and spaced inwardly fromthe tread surface.
 4. A tire tread according to claim 2 wherein the endsof said crossbars slope upwardly tapering and merging into the sidewalls of said grooves being formed generally in crescent-shapedcross-section transverse of said groove.
 5. A tire tread according toclaim 2 wherein said crossbars are triangular in cross-section, the apexof which triangle being disposed radially outwardly from the base of thegroove.
 6. The tire tread according to claim 2 wherein the surface ofsaid crossbars is generally curved.
 7. A tire tread according to claim 2wherein at least one end of the radially outer surface or extremity ofat least one of the crossbars extends radially outwardly to mergegradually with the wall of the groove.
 8. A tire tread according toclaim 2 wherein at least one of the crossbars extends across the wall ofthe groove and is generalLy U-shaped in cross-section transverse to thegroove.
 9. A tire tread according to claim 2 wherein the depth of theU-shaped crossbar gradually decreases towards its junction with the wallof the groove adjacent to the tread surface.
 10. A tire tread accordingto claim 2 wherein the radially outer surfaces or extremities ofalternate crossbars extend respectively from opposite walls of thegroove radially inwardly from a junction of the said surfaces orextremities of the crossbar with the wall of the groove adjacent to thetread surface.
 11. A tire tread according to claim 10 wherein theradially outer surfaces or extremities of alternate crossbars extendfrom a junction with the wall of the groove spaced from the treadsurface.
 12. A tire tread according to claim 10 wherein the radiallyinner surface of the two junctions of the radially outer surface orextremity of the crossbar with the walls of the grooves is spaced apartfrom the groove bottom.
 13. A tire tread according to claim 2 wherein atleast one of said crossbars is rectangular in cross-section.
 14. A tiretread according to claim 2 wherein at least one end of the radiallyouter surface or extremity of at least one of the crossbars extendsradially outwardly to merge gradually with the wall of the groove.
 15. Atire tread having a traction pattern including grooves, crossbarsextending laterally across the bottom of said grooves, and the spacingbetween said crossbars being no greater than the width of said grooves,a recess defined by the tops of said crossbars and the inner wallportions of said groove for receiving without retaining particles, thespacing between said crossbars being no greater than the width of saidcrossbars, said spacing being measured either at the base of the grooveor at the top of the crossbar, whereby particles of size greater thanthe spacing between the crossbars are cradled from the bottom of saidgroove and smaller particles which may enter said recess are notretained therein, and wherein the radially outer surfaces or extremitiesof alternate crossbars extend respectively from opposite walls of thegroove radially inwardly from a junction of the said surfaces orextremities of the crossbars with the wall of the groove adjacent to thetread surface.
 16. A tire tread according to claim 15 wherein theradially outer surfaces or extremities of alternate crossbars extendfrom a junction with the wall of the groove spaced from the treadsurface.
 17. A tire tread according to claim 15 wherein the radiallyinner surface of the two junctions of the radially outer surface orextremity of the crossbar with the walls of the grooves is spaced apartfrom the groove bottom.